Allow me to introduce myself and the suggested contribution to the SSSD
project. PrimaryData Inc. is a startup company in the field of distributed
NAS. As such, we would like to contribute to the SSSD project by developing
support for rpc.idmapd.
Below is our proposed design for this new feature.
*SSS NFS Client (rpc.idmapd plugin) - Design*
We named the client "sss_nfs" (althogh "sss_idmap" or "idmap" might have
been better names, the term "idmap" is already occupied in the SSSD world).
*rpc.idmapd - background*
rpc.idmapd runs on NFSv4 servers as a userspace daemon (part of nfs-utils).
It's role is to assist knfsd by providing the following 6 mapping functions:
1. (user) name to uid
2. (group) name to gid
3. uid to (user) name
4. gid to (group) name
5. principal (user) name to ids (uid + gid)
6. principal (user) name to grouplist (groups which user are member of)
rpc.idmapd provides API for developing plugins (loaded by dlopen(3)) which
implements the actual mapping process.
* note: 5 + 6 are relevant only for kerberised NFSv4 servers. At the first
stage we only purpose a design without kerberos support.
* note2: On the kernel level, there's a caching mechanism for the responses
from the userspace daemon.
*SSSD - Responder*
The functionality required from the Responder side is a subset of the
functionality provided by existing NSS Responder's commands.
As you can see below (on the client part of the design) - no changes are
needed in the NSS Responder.
*SSSD - NFS Client*
*Responder-Facing Interactions (existing NSS Responder commands)*
SSS_NSS_GETPWNAM - map (user) name to uid requests
SSS_NSS_GETGRNAM - map (group) name to gid requests
SSS_NSS_GETPWUID - map uid to (user) name requests
SSS_NSS_GETGRGID - map gid to (group) name requests
The request & reply sent to & from the responder is "standard" in terms of
the NSS Responder.
The client only needs a portion of the reply. Only this portion will be
extracted from the packet (i.e. uid/gid/user name/group name).
The optimisation techniques used for the NSS client will be used here as
well. i.e. Fast Cache (memcache) & negative-cache.
It will be possible for the user to disable Fast Cache from the
configuration file. (see below)
The configuration of the client will be part of rpc.idmap config file
*Linux Software Engineer*
P.O. Box 12650, Herzliya Pituach 4673300
9 Hamenofim St. Akerstein Towers, Tower A, 5th fl. Herzliya
Office: +972-77-8981888 | Fax: +972-3-7617140 | Mobile: +972-54-5873843